Studies are in progress to investigate various aspects of the genetic control of the immune response. We are planning to transfer the Ir-2b dominant nonresponder gene from the NS30 congenic strain to B10, which will allow us to determine whether Ir-2 is a histocompatibility locus. We are also developing a congenic line of Fischer rats which will have the Ag-B3 allele of BN, in order to study an Ag-B-linked gene which controls susceptibility to experimental allergic encephalomyelitis. BIBLIOGRAPHIC REFERENCES: Knisely, A.S., Gasser, D.L. and Silvers, W.K. Expression in Organ Culture of Agout Locus Genes of the Mouse. Genetics 79:471-475 (1975). Gasser, D.L., Palm, J. and Gonatas, N,K. Genetic Control of Susceptibility to Experimental Allergic Encephalomyelitis and the Ag-B Locus of Rats. J. Immunology 115:431-433 (1975).